I don't think a 1 gallon is necessarily too small. If the fish is happy and you can keep up with the water changes I think they're fine. I don't have the space for a large tank and keep two boys in a divided 2.5 gallon (although I'm eventually going to upgrade to a divided 5.5). They are both happy and content fish
. As long as water is good and quality foods are fed a 1 gallon isn't bad IMO. But it does depend on the fish too, they all have such individual personalitys its one of their best traits.